Humidifying equipment having porous hydrophobic water channels or conduits, and fans or other means to blow air across the porous surfaces of the conduits are known in the art.
The water conduits may be made of porous hydrophobic tubing or, in other cases, laminated constructions of porous hydrophobic sheet. The porous hydrophobic materials used as humidifier water conduits resist passage of liquid water through them, but permit passage of water vapor through them, thus humidifying the air stream passing over the porous surfaces. Polymeric materials used for the hydrophobic tubing or sheet include polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyester, or fluoropolymers.
Porous hydrophobic tubing or sheet of the above materials, although having good initial water repellency and resistance to passage of liquid water through their pores, can lose their water repelling ability due to contamination or degradation caused by oily materials, surfactants, detergents, and the like, with which they come into contact in the course of their manufacture or use. When this occurs, water begins leaking from the conduits, leading to failure of the humidifiers.
An additional problem with such humidifying equipment is that during the initial charging of water into the conduits, or during subsequent normal usage, air pockets form in the conduits which resist displacement by the water. This results in lower evaporation rates and reduces the efficiency of the humidifiers.